(Reuters) - President Donald Trump’s nomination of Brett Kavanaugh to the U.S. Supreme Court is now in the hands of the Senate, where the opposing forces are clear, except for a few senators who sometimes cross party boundaries, depending on the issues.

FILE PHOTO: Chairwoman Lisa Murkowski (R-AK) speaks during a hearing of the Senate Committee on Energy and Natural Resources on Capitol Hill in Washington, U.S. March 13, 2018. REUTERS/Eric Thayer/File Photo

Confirmation of Kavanaugh will require a simple majority in the 100-seat chamber. The Republicans hold a 51-49 edge over the Democrats and independents. Republican Vice President Mike Pence can cast a deciding vote in the case of a tie.

If the Republicans all stick together, they can get Kavanaugh confirmed, but that may be a challenge, given the divisive issues swirling around the conservative nominee, including abortion, gay rights, health care and tariffs.

REPUBLICANS

* Susan Collins of Maine said on July 1 she would not support a Supreme Court nominee “who demonstrated hostility to Roe v. Wade,” the 1973 high-court decision legalizing abortion.

Since then, the four-term senator has said Kavanaugh is “qualified” to become a justice, but that she needed to learn more about his judicial temperament and philosophy.

* Lisa Murkowski of Alaska has promised to be “rigorous” in her review of Kavanaugh’s record.

Like Collins, her support of abortion rights has led some Democrats to believe Murkowski could vote no. Also like Collins, Murkowski helped ruin Trump’s 2017 bid to fully repeal Obamacare. But earlier that year she voted for Gorsuch.

* Rand Paul of Kentucky is a failed 2016 presidential candidate and party renegade. Since Trump nominated Kavanaugh on July 9, Paul has waived off throngs of reporters seeking hints of how he will vote. “I’m keeping an open mind and we’ll follow the process,” Paul said tersely on July 10.

* John McCain of Arizona, among Trump’s harshest critics, has been away from Washington this year for treatment of brain cancer. He has praised Kavanaugh, but if McCain is physically unable to return to the Senate for the confirmation vote, Kavanaugh’s path to approval could be narrower.

DEMOCRATS

* Heidi Heitkamp of North Dakota is among Senate Democrats running for re-election in November in states that heavily supported Trump in 2016. She was one of three Democrats who voted for Gorsuch. Joe Manchin and Joe Donnelly were the others.

Heitkamp, a first-term senator, has mainly been keeping her head down in the early days of the Kavanaugh debate.

* Joe Manchin of West Virginia is making healthcare his main consideration in whether to support Kavanaugh. Democratic leaders say Kavanaugh will rule against Obamacare the first chance he gets on the Supreme Court.

Kavanaugh dissented in a 2011 federal appeals court decision that found Obamacare did not violate the U.S. Constitution. But Kavanaugh’s dissent was narrowly crafted and did not address the law’s constitutionality.

* Joe Donnelly of Indiana is one of the most threatened Senate Democrats in November’s elections. He is walking a political tightrope and trying not to offend the large Trump constituency in his state, where Pence was governor before becoming vice president. So far, Donnelly has said he will carefully review Kavanaugh’s record and qualifications.

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* Claire McCaskill of Missouri is being discreet, saying she will examine Kavanaugh’s record. With a tough re-election ahead in a heavily Republican state, McCaskill, a former prosecutor, is quick to point out she has voted for more than two-thirds of Trump’s judicial nominations. She voted against Gorsuch.

* Doug Jones of Alabama jolted U.S. politics last December in a special election by becoming the first Democratic senator elected from the southern state in over two decades. To get re-elected in 2020, Jones, another former prosecutor, must show he can be an independent-minded Democrat. The Kavanaugh vote could be a test.

Jones was not in the Senate when it voted to confirm Gorsuch. In his short Senate career, Jones has supported Trump judicial nominees when there was little controversy and opposed them in other instances. Jones said he will undertake “an independent review” of Kavanaugh.